Hey folks, I need some input on how to tackle the problem I am having with my rebuilt 8RT flathead engine. The engine was torn down and machined by a reputable shop 15-20 years ago, then once the machining work was done my dad took the block home and boxes of parts for it and assembled it. I don't think my dad had assembled a flathead before, but he was very good about reading instruction manuals, and had experience with assembling engines in the past. The assembled engine was installed in the truck but never tried starting it as the restoration was still under way with the rest of the truck. Well, my dad passed away around 12 years ago, so the truck has ended up in my hands to finish the restoration on and get it going again.

Reached the point of attempting to get the engine running about 4 months ago, and I was able to start it, but it ran very rough like it was missing, figured the timing was off or something like that. But also there was a lot of smoke coming out of the oil fill port. Probably only got about 5 minutes total of run time on it that day. Anyway, I just got back to working on it again today. Did a compression check, and am getting 55-75 psi on the cylinders with the throttle open. Squirting oil in the cylinders gets them all up to around 120-125 psi. Also utilized a leak down tester and didn't notice any loss through the valves, but the air is escaping fast down into the crankcase. At 90 psi on the input gauge I am only seeing about 20 on the output gauge so it is barely building any pressure in the cylinders.

Now with virtually no run time on the engine, the rings wouldn't be seated fully yet, but is it normal to be that far off? Am I at the point of tearing back into the engine to see what is going on?

Maybe the rings are the wrong ones for the pistons, or the pistons are the wrong size for the cylinders? Seems that dad would have caught something like that during the assembly if the machine shop handed him the wrong sized parts, but who knows at this point. Also perhaps a completely unrelated problem is that there is oil showing up in the coolant, but no coolant in the oil.

So, where to go from here? Thanks in advance for any suggestions you guys can provide me with.

 

If the storage environment was that of heat and cool with any kind of humidity, I would suspect there are some rings stuck. if it were me, I would run the engine at high idle while feeding some solvent of some kind slowly thru the carb. Perhaps some on here will make a recommendation for a brand of snake oil to use. Good luck. I would see if the coolant cleaned up when the compression comes back and the engine runs correctly. A slight oil film is not uncommon.

 

Do you know what type of rings your dad used (chrome or cast iron)? Since your compression numbers are even, I'd put the low numbers down to not being seated, chrome rings take a while. With your humidity up there, it's possible the cylinders have a fair amount of surface rust, can you check for that with a scope? The rust may also have gotten scraped off and is holding the rings like Ray said. Depending what you see, I'd consider yanking the heads, and pan, and whatever else to clean the cylinders, pistons, and rings/grooves. MUCH cheaper than potentially scoring cylinders.

On the other hand, some people would give a good run under load before going to that extreme. Again, if the borescope looks good, that would be easy to do and has a good chance of success.

 

I’m going to guess cast rings since this was a mostly stock build. But can’t say for certain. As for putting a bore scope down in there, I tried that but there isn’t enough space to make the angle down into the cylinder unless there is a trick that I am missing. What I can see looks clean with no rust. Humidity is generally reasonable here in Southern Oregon, but for the most part the truck has been stored in an unheated garage, so there have been plenty of heating and cooling cycles over the years that could have produced enough condensation to cause rust.

 

Its my guess you are using a bora scope with an 8mm head....5.5mm ones are available and will go where the 8mm can not....I bet there is considerable surface rust...I would open her up for inspection and clean up...

 

8mm is probably about right. It is a Snap-on BK3000. I’ll have to look, but I don’t think the head is removable to put a different one on there.

Rather than spend a bunch of money on a completely different inspection camera system since I barely even use this one once a year, I would probably just pull the heads off to get a better look in there.

 

Head gaskets are relatively cheap, for the peace of mind you might get from a look inside.

 

So, lets say I pull the heads off and find some surface rust. What would be the best way to clean everything back up so the rings seal properly?

I do remember my dad using some special oil or something in there on assembly because he was expecting the engine to sit for a couple years before being started, and the machine shop had told him that using whatever it was should allow it to sit for quite some time and keep rust from being a problem.

I'm really tempted to put some oil down the holes to get the compression up then try firing it up again. The last time I had it running even though it was running poorly it seems like I was fighting some fueling issues at the same time so never had it going for more than a minute or so each try. But even if was able to get it running somewhat decently, I don't have a way to put it under load since the truck isn't really drivable in its current state just yet.

Every time I've worked on this truck recently it feels like one step forward, three steps backward. Probably just the way it is with most restorations, but it sure is frustrating!

 

That compression should be enough to fire it. If the carb has sat for some time especially with fuel in it, it’s probably gummed up. I would clean that carb and put a new kit in it.

JB

 

There is no real point to getting it running, unless it can be put under load and properly broken in. Even if you do that, if it is just going to sit another year or more, you will end up at nearly the same place. What are your long-term plans for the truck? If you are just assembling to sell it, by all means throw some 10wt oil down the holes and crank it with no spark plugs to make sure the rings are lubed and freed up, build oil pressure with 10w30 in the crankcase, then fire it up.

 

This is not an assemble and sell project. The purpose of getting the engine running is to make sure I have everything right before starting on the front sheetmetal, because I don't want to scuff that up while chasing engine issues. If the engine has to come back out for whatever reason, now is the time to figure that out. Yes, it will probably be another year or so before the truck is able to be out on the road, but if I can get the engine to run properly now, then at least I can start it up once a month or so and run it for 15 minutes at a high idle to keep everything properly lubricated in there.

If this is a bad plan, I would appreciate ideas on the best approach. Thank you!

 

Why not wait to put the sheet metal on until you can drive it, even if it is while sitting on a bucket or lawn chair? Where exactly is the truck in terms of completeness? Is the cab on, seat in place?

Any time you run an engine (especially a new one) you want to get the water and oil up to full temperature, or you risk building sludge. 15 minutes at high idle won't likely get you there, and until the rings are seated, will just wear them out. They need pressure from load. I understand your goal but there's risk either way. Does a shop around there have a dyno?

 

Well, in that case I suppose it is in driveable condition. I could sit on a milk crate and run it around the farm in second gear. Don’t know if that is enough load since it’s not highway speeds, but it might be enough of a quick shakedown test? Or tie it off to a tractor and pull the weight around a bit?

 

Highway speeds aren't needed or desirable. Do you know if your dad replaced the cam? I think you would want to assume it needs to be broken in first thing, at a fast idle for at least 5 minutes.

Hastings Piston Rings used to have an excellent procedure for seating rings, that went like: quickly accelerate from 10 mph to 30 mph in 2nd gear with a lot of throttle (builds pressure), coast down, repeat 4 - 5 times, then run it up higher and higher on later runs. Finally run it through a normal drive cycle. (If you have a crashbox 4-sp, you'd likely use 3rd gear, not 2nd). Towing the tractor would work, at lower speeds for safety, if you don't have a country road at hand. Good luck!